LINDA A. JOHNSON AP Business Writer TRENTON, N.J. (AP) — New studies show GlaxoSmithKline PLC's vaccine Cervarix blocks the virus that causes cervical cancer, but if it wins approval for U.S. sales, it will face an uphill battle against Gardasil, which has owned the market here for three years. Cervarix, Glaxo's vaccine against human papilloma virus or HPV, already is approved in more than 90 other countries, but has been held up by delays in the United States. Several years ago, the British drugmaker was in a neck-and-neck race with rival Merck & Co., Gardasil's maker, to be first on the U.S. market, but it lost when Gardasil got approved in June 2006. Late in 2007, U.S. regulators said they wouldn't approve Cervarix without additional data. from a large study still in progress at the time. Final results from that 18,000-woman study and two others are being presented this weekend at a conference in Sweden on papillomavirus. The data was submitted to the Food and Drug Administration on March 30, and FDA is expected to decide whether to approve Cervarix within several months. If it does, analyst Erik Gordon, a professor at the University of Michigan's Ross School of Business, said doctors who have prescribed Gardasil for a few years may see no reason to switch — unless GlaxoSmithKline convinces them its product is much more effective or has fewer side effects. Both vaccines target the two types of HPV that cause about 70 percent of cervical cancers, types 16 and 18, and data indicate both are about 98 percent effective. But Merck also has data showing Gardasil blocks two other HPV types that cause most cases of genital warts that Cervarix does not target. That will be a key factor for doctors, experts said. "All else being equal, it's a no-brainer for the doctor, (who) wants to give the most efficacious treatment," Gordon said. Despite Merck owning the U.S. market, Gardasil racked up only $262 million in global sales in the most recent quarter, versus $320 million for Cervarix, which has won more contracts from government health programs in other countries. Partial results of the new Cervarix studies released to The Associated Press indicate it also offers good protection against 12 other HPV types. One of the studies, which looked at looked at levels of antibodies to some HPV types after study participants were vaccinated with Cervarix or Gardasil, found higher antibody levels induced by Cervarix. But Dr. Gary Dubin, head of one of Glaxo's clinical development centers, said that doesn't prove Cervarix is more effective. New data will be presented at the same conference on Gardasil, indicating it blocks HPV 16 for at least 9 1/2 years, according to Merck. Glaxo has followed women for up to 7 1/2 years and continues to test some to see if they develop cervical lesions or cancer. Dr. Cynthia Rand, a researcher, pediatrician and associate professor at the University of Rochester Medical School, said Cervarix appears to be effective. But she said the higher antibody levels triggered by Cervarix, compared with Gardasil, might be meaningless. She said doctors don't know if they will have to give booster shots years from now for either vaccine. "It won't change my practice" of giving Gardasil and likely won't do so for other doctors, said Rand, whose university has patent claims and receives some royalties related to both vaccines. "Pediatricians prefer in general to also protect against genital warts."